1. Field of the Invention
This invention relates to mirrors in general and in particular to a plastic film mirror produced by a heat shrinking process.
2. Description of the Prior Art
In recent years a substantial market has developed for mirrors for residential use, in addition to the traditional uses of mirrors on dressing tables, medicine cabinets and the like. Mirrors have become popular on closet doors, both of the opening and sliding variety and a market is developing for reflective ceiling and wall tiles, both having a decorated and undecorated reflective surface.
One of the disadvantages of glass mirrors is the problem of high breakage and weight. The solution to this problem requires expensive and heavy packaging, which adds to the already substantial freight costs involved in the long distance shipment of glass.
A second disadvantage, which is an esthetic one, is that the principal reflective surface of a traditional mirror is behind a layer of glass. Thus, the reflection of such mirrors is not as bright as would be possible if the reflective surface were on the front face of the mirror rather than the rear face. Due to problems of technology it has not generally been practical to place the reflective coating on the front surface of glass. Although, of course, this technique is employed in nondomestic applications such as astronomical telescopes and the like.
The discovery that a stable, smooth, reflective surface could be obtained by the vacuum deposition of certain metals upon certain plastic materials led to the use of such materials as mirrors. In order for such mirrors to be formed and to maintain good plainer reflective surfaces, it is necessary that the reflective surface be permanently under tension. A substantial amount of work has been done in this area and will be found in U.S. Pat. Nos. 3,434,181 and 3,552,835 to Benzies and U.S. Pat. Nos. 3,608,179 and 3,180,220 to Jeffree et al. A review of these patents will show that an essential component of these mirrors is a tensioning and tension-retaining means such as a vacuum pockets rigid or semirigid ring spring or similar device. The use of such devices complicates the structure of the mirror and increases their costs, both from the point of view of materials and from the point of view of structural complexity. It would be highly desirable, therefore, to provide a mirror which has the general properties of the Benzies and Jeffree mirrors, without the necessity for their structural complexity.
Heretofore, the deposition of preformed films upon frames in order to produce sealed surfaces and the like, has been known. A representative example of this technique will be found in Demke U.S. Pat. No. 3,154,435, which deals with the formation of a membrane faced acoustical tile. Similar techniques have been employed in the packaging method generally known as "bubble coating" wherein an article to be packaged is placed upon a base, usually a coardboard base, which is either somewhat permeable to the passage of air or has a plurality of pinholes therein. A plastic film, usually a polyethylene film, is soften and laid over the device to be packaged and the backing card and a vacuum applied to the back of the card, whereby the device is substantially envelope in the plastic, which also adheres to the card.
Heretofore, however, it has not been possible to coat low softening point plastics, such as polyethylene with a reflective coating. The reason for this is believed to be that in the first place vacuum coating requires somewhat elevated temperatures at which film such as polyethylene cannot be held under tension, a requirement for even coating, and secondly even if this were possible, there is a danger that under these conditions the plasticizer in the film would outgas in such a manner as to form bubble imperfections in the metalized film.